The jury is still out on Negative SEO, but in order for negative seo to work there has to be a way for Google to find out sooner rather than later about those bad links. Its good news for the Negative SEOers that a Google spam reporting tool is available.

Snitching is the Last Step in the Negative SEO Process
"After building a base of horrible backlinks whose sole intention is to put your competitor in 'bad neighborhoods', report those links to Google. Rinse, repeat for all websites above yours." - Advice from a Black Hat SEO.

I don't think Google should have a campaign of asking you to turn in your parents, friends and especially your enemies for spam.

Search Engines Should Determine Spam with People and Automation not Snitches
How often have we seen poor quality websites come from out of nowhere because they bought thousands of 'good' links. Now people are buying 'spam' links to hurt their competition with Google penalties.

The post-Penguin reporting tool is giving black hats another tool in their arsenal.

Another knife in the back of the competition? Does this not go against the 'Don't be evil' Google slogan?

Very few people in the world know anything about reporting spam. SEO's do. And now thanks to promoting snitching by Google, the evil newbies do too.

No one else is going to report spam, just the good, the grey and the bad. But mostly the bad. Google needs to fix this by not being reliant of those whose intent is to do evil.

How do you separate the good spam reports from the evil ones? What angel at Google will handle these reports and pass judgement on the target from an anonymous tipper? How can a system of humans be kept away from corruption when millions, perhaps billions of value are at stake?

I would like to see Google minimize talk about spam reporting and maximize communication through webmaster tools. If you suppose a back link is SPAM, tell us through webmaster tools. Any white hat webmaster would take a serious look at the link and do something about it or defend the link.